Christ says His words are Spirit and Life; they have a quality above human words because their source is divine. If ingested, these words lead to eternal life.
When God speaks, His words are never futile or useless. He never utters a word in vain. Genesis 1 shows what resulted from God speaking just a handful of sentences!
God's Word causes things to increase just as rain causes crops to increase, but the increase is not always numeric. Often, it is qualitative.
Eternal life is to live a quality life as God lives, having developed a close relationship with God, living by faith and accepting His sovereignty over all.
The ancient Israelites resisted the gospel, refusing to mix it with actual obedience. What they heard never became a part of their lives; Egypt never left them.